Devices and systems have been developed for use in various body lumens, particularly in the cardiovascular system, digestive, and urogenital tract. Catheters are used for performing a variety of sensing and material delivery tasks. Stents are implanted in blood vessels for the purpose of preventing stenosis or restenosis of blood vessels. Capsules containing sensing and imaging instrumentation that may be swallowed by a subject and which travel passively through the digestive tract have also been developed. Robotic devices intended to move through the lower portion of the digestive tract under their own power are also under development.